This invention relates to the separation of sulfur compounds from mineral oils, and more particularly to the use of a special sorbent and to its regeneration after use.
Generally, sulfur occurs in petroleum and syncrude stocks, tar sand oil, shale oil and the like, in such forms as organic mercaptans, sulfides, disulfides, and as a part of ring compounds such as thiophene, benzothiophene, and dibenzothiophenes and the like impurities. Usual practice in petroleum and syncrude refining is to remove at least the major portion of these impurities from the oil or from product fractions obtained from the oil, such as straight-run, gas oil, vacuum gas oil or the like fractions. Normally sulfur removal is by treatment using hydrogen and a catalyst under well-known hydrotreating, hydrofining and/or hydrodesulfurizing conditions. In general, the cost of sulfur removal by such treatments in terms of hydrogen consumed, light gas make, reduced catalyst life and the like costs, increases markedly with increasing degree of sulfur removal. When the mineral oil originally has but a minor content of sulfur or has been hydroprocessed to such a low sulfur content, for example in the range from 1 to 500 ppmw, catalytic hydroprocessing or further hydroprocessing may be uneconomical in terms of efficient usage of a costly catalyst. Consequently, there is a need for an effective means for removing a minor amount of sulfur-containing impurities from a mineral oil, especially of the residual impurities in a hydroprocessed oil. These impurities in general, or at least in large part, are of the thiophene type, for which relatively severe process conditions are usually required for their hydrogenative desulfurization.
It is an object herein to provide an effective regenerative sorbent process for removing residual and/or trace amounts of sulfur-containing impurities from a mineral oil.